Spark plug



Jan. 31, 1928. 1,657,863

W. MCELROY v SPARK PLUG Filed NOV. 22. 1926 INVENTOR.

I AT RNEYS.

. Patented Jan. 31, 1928.

UNITED STATES WILL! MoELB-OY, OI BROOKLYN, NEW YORK.

SPARK PLUG.

Application filed November 22, 1926. Serial No. 149,848.

This invention is a spark plug and the object of the invention is to provide a plug which will last indefinitely. This is made possible in accordance with this invention by providing renewable electrodes. That is to say, the central or insulated electrode of the plug may be readily renewed without disassociating the porcelain from the shell of the plug. and the same is also trueof the grounded electrode. In practically carrying out the invention, I provide the insulator of the plug with a straight through passage and on thetop of the insulator a thimble is mounted provided with a continuation of this passage and having a threaded shank on which a terminal cap may be screwed. When the terminal cap is removed, an un obstructed passage is uncovered which leads directly through the insulator and into this passage the insulated electrode is ada ted to be inserted. This electrode is forms at its upper end with a cylindrical head, which,

when the electrode is positioned within the passage, is adapted to be partially received within a pocket in the top of the thimble and seat upon a gasket in the base of said the thim le and .forms a Positive lock to hold the parts in assembled relation.

With this arrangement, it is possible to substitute a new electrode for one which has been worn out by merely removing the terminal cap, and substituting the new electrode for the old. one and this may be accomplished without removing the plug from the motor.

The grounded electrode may be of difi'erent forms. Inone of its practical forms, it embodies a yoke constructed of wire and extending transversely of the en bottom of the plug shell. One end 0 the wire is bent at substantially right angles to the remainder of the wire and extends into a socket in the shell, while the other end of the wire is adapted to engage with a hook shaped keeper mounted substantially diametrically across the shell from said socket so that the yoke can be engaged with and disengaged from the hook, after the manner of opening and closing a safety pin. So long as it is engaged with the hook, the yoke cannot be detached, but when it is disengaged from the hook it may be lifted out of the socket to permit of the substitution of a new oke.

A p ug is thus provided having readily removably electrodes and inasmuch as it is the electrodes of the plugs which are subjected to wear and cause depreciation and failure of the plug to properly operate, it becomes apparent that by providing readily renewable electrodes, a plug of interminable life is provided.

Features of the invention, other than those specified, will be apparent from the hereinafter detailed description and claims, when read in conjunction with the accompanying drawings. v

The accompanying drawings illustrate difierent practical embodiments of the invention, but the constructions therein shown are to be understood as illustrative, only, and not as defining the limits of the invention.

Figure 1 is a central vertical section of a spark plug embodying the present invention.

Figure 2 is a bottom plan view of the plug of Figure 1. 1

Figure 3 is a fragmental elevation of the upper portion of the plug showing the terminal cap in section. 1 I Figure 4 is a side elevation showing the central electrode removed from the plug.

Referring to the drawings, 1 indicates the insulating element of the plug which, in practice, is generally porcelain or mica of substantially conventional form. The porcelain is suported in a suitable metallic shell 2 and is shown'as held in place therein by a j amb nut 3 in the conventional manner.

Secured to the top of the porcelain in any suitable manner as by spinning is a thimble 4 provided with an upstanding tubular exteriorly threaded shank 5 having therein a coaxial pocket 5. The passage through this shank is juxtaposed with the electrode channel 6 of the porcelain, so that when the parts are assembled an unobstructed passage will extend from the top of-the part 5 to the bottom of the porcelain. Into this passage, a central electrode 7, shown in Figure 4, is adapted to be introduced. This central electrode is provided at its top with a rigidly attached substantially cylindrical head 8 which may be formed with an annular channel 9. f

The electrode is introduced into the plug by droppin it through the passage in the thimble and porcelain whereupon the head will come to a seat in the base of the ocket 5 on a gasket 10 positioned therein. A terminal cap 11 provided at its top with a binding post 12 for the ignition lead is adapted to be screwed down upon the threaded shank 5 to produce a tight joint between the head and said gasket. This operation will effect a good electrical con tact between the electrode and the thimble and cap, such as to preclude arcing at this point. To preclude the cap from jarrin loose a split ring lock washer 13 is positione( between the base of the cap and the thimble 4, as shown in Fig. 3. This type of lock washer is used in this connection so as to permit an eflicient seating of the head of the electrode and to simultaneously effect a tight lock. In practice, the electrode may be readily removed from the plug when it becomes worn and a new one slipped in place in an easy and expeditious manner, and without necessitating the removal of the plug from the motor. The annular channel 9 is to permit the head 8 to be more easily gripped during this operation.

The preferred form of grounded electrode used in conjunction with the insulated electrode which I have described, is shown in Figures 1 and 2 of the drawings. Here, a yoke 14 constructed from .wire embodies a substantially straight horizontal tongue portion 15 with an n turned end 16. The upturned end exten s into a socket 17 in the lower edge of the shell and the free end ofis accom lished after the manner of operating a ety pin.

he yoke is provided intermediate its ends with an upwardly extending hump 19, as shown in Fig. 1, so as to permit oil to gravitate away from the ga It will be understoo that as long as the yoke is in engagement with the hook 18, it is recluded from pulling out of the socket 17, ut if the yoke is disengaged from the hook, it may be readily lifted out of the socket and a new oke substituted. This arrangement is highly efiicient and provides a readily changeable grounded electrode well a apted to cooperate with the renewable central electrode which I have described.

It will be apparent from the foregoing detailed descriptnon of the invention, that I rovide a lu which can be used for such 1 ong perio s that the In will last for substantially the life 0 t e motor, b the changing of the electrodes as may re quired to maintain the plu in proper working order. The construction which brings about this novel result is unusually simp e and economical as to first cost and subsequent maintenance.

The drawings show the invention in its preferred practical form but the invention is to be understood as fully commensurate with the appended claims.

I have particularly referred to the removability of the electrodes to enable them to be replaced in the event of undue wear and the 1 requirement for placement. I find, in practice, however, that the ability to remove these electrodes greatly facilitates the cleaning of the plug and this particularly ap lies to the central electrode, which, because 0 the structure shown and described, may be readily slipped out for cleaning purposes and if too badly worn may be replaced with a new one at the same time.

Having fully described the invention, what I claim as new and desire to secure by Letters Patent is:

1. A spark plug embodying a central electrode, and a grounded electrode embodying a tongue, one end of which is adapted to seat within a socket in the bottom of the plu" shell, and a hook shaped retainer adapter to detachably engage the free end of the tongue to maintain the tongue againstdisengagement from the socket, said tongue being manually disengagcable from the hook shaped retainer to permit removal of the grounded electrode.

2. A s ark plug having a orcelain provided with a straight througi assage extending axially thereof, a thim le with a skirt fitted over the top of the porcelain and permanently and rigidly secured thereon, said thimble having a tubular exteriorly threaded shank coaxial and alined with the assage through the porcelain and provided 1n its' top with a cylindrical pocket, a gasket at the base of said pocket, a central electrode comprising a rod, the upper end portion of which is provided with a substantially cylindrical head to seat on the gasket in said pocket and sufliciently high to extend above the top of the threaded shank and dprovide a finger, iece which may be graspe to withdraw t e electrode, and a threaded terminal cap screwed on to the threaded shank of the thimble to force the head of the electrode to a firm seat on said gasket and to simultaneousl insure good electrical contact between the ead and the cap.

I In testimony whereof I have signed the foregoing specification.

McELBOY. 

